U.S. Pat. No. 3,833,408, herein incorporated by reference, describes the application of methyl alkyl siloxane compositions as lubricants for conductive video discs comprising a molded plastic disc having audio and video information in the form of geometric variations in a spiral groove. These discs are coated first with a conductive material which acts as a first electrode, then with a dielectric layer and a final layer of lubricant. A metal tipped stylus acts as a second electrode of a capacitor and the information signals are monitored by the stylus which notes changes in capacitance between the stylus and the disc surfaces as the information, in the form of depressions, passes beneath the stylus.
Further developments in this system have produced a video disc which is made of a conductive plastic material, e.g., a PVC copolymer resin containing sufficient amounts of conductive carbon particles so that the disc can provide capacitance readout, while the plastic resin surrounds the carbon particles providing a dielectric surface layer on the conductive particles. This development has eliminated the need for separate coatings of metal and dielectric on the plastic disc.
The stylus, formerly made of metallized sapphire, has also been improved so that metallized diamond can be used. Diamond is a harder, longer wearing material than sapphire, and also requires good lubrication of the disc surface.
Video discs are also being developed which do not require a conductive surface or a grooved surface, the stylus being maintained in synchronization with the information pattern track by means of electrical signals rather than the groove walls.
These changes in the materials used for the video disc and stylus have somewhat changed the requirements for the lubricant and in certain respects the commercially available methyl alkyl siloxane lubricant is now unsatisfactory. One commercially available methyl alkyl siloxane composition has the formula ##STR2## wherein R is a straight chain decyl group, and n is an integer. This material has a molecular weight of about 1500 and a viscosity of about 50 centistokes and is sold by General Electric Company as SF-1147. This composition also contains about 1.5 percent of antioxidant compounds.
When the present video discs molded from carbon-loaded PVC compositions are spray coated with the SF-1147 lubricant and played back with a diamond stylus, the playback performance and stability are less than desirable. Thus an attempt was made to improve the performance of this class of lubricant and the present invention resulted.